package test;

public class HW {
}
class Base{
    public Base(String s){
        System.out.print("B");
    }
}

class Derived extends Base{
    public Derived (String s) {
//        super(s);                 //必须先构造父类
        System.out.print("D");
    }
    public static void main(String[] args){
        new Derived("C");
    }
}